Java - using JavaMail to send an email to the user's mailbox

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Send an email via javamail:
Earlier, I had written a tool class MailUtils for sending mail. The following points need to be noted:
① The mail server address of the Outbox.
② Outbox account number.
③ Mailbox authorization code, which is set in the used mailbox background management.
④ Address of the activation message.